There is general agreement that glucose tolerance deteriorates with age, and the goal of the proposed research is to learn more about this phenomenon. The experiments outlined in the proposal will be carried out in normal man, and will attempt to define the effects of age on plasma glucose and insulin response to an oral glucose challenge, insulin secretory response to infused glucose, the ability of insulin to dispose of an infused glucose load, and numbers and affinity of insulin receptors on adipocytes. The results of these studies will be correlated with estimates of obesity and level of physical activity in order to evaluate the effect of both age, and age-related variables, on glucose tolerance.